We present the analysis of supernova remnants (SNRs) in the Large Magellanic Cloud (LMC) and their influence on the environment at far-infrared (FIR) and submillimeter wavelengths. We use new ...observations obtained with the Herschel Space Observatory and archival data obtained with the Spitzer Space Telescope, to make the first FIR atlas of these objects. The SNRs are not clearly discernible at FIR wavelengths; however, their influence becomes apparent in maps of dust mass and dust temperature, which we constructed by fitting a modified blackbody to the observed spectral energy distribution in each sightline. Most of the dust that is seen is pre-existing interstellar dust in which SNRs leave imprints. The temperature maps clearly reveal SNRs heating surrounding dust, while the mass maps indicate the removal of 3.7+7.5-2.5 M ☉ of dust per SNR. This agrees with the calculations by others that significant amounts of dust are sputtered by SNRs. Under the assumption that dust is sputtered and not merely pushed away, we estimate a dust destruction rate in the LMC of 0.037+0.075-0.025 M ☉ yr-1 due to SNRs, yielding an average lifetime for interstellar dust of 2+4.0-1.3× 10^7 yr. We conclude that sputtering of dust by SNRs may be an important ingredient in models of galactic evolution, that supernovae may destroy more dust than they produce, and that they therefore may not be net producers of long lived dust in galaxies.
ABSTRACT We present new Hubble Space Telescope images of high-velocity H and Ly emission in the outer debris of SN 1987 A. The H images are dominated by emission from hydrogen atoms crossing the ...reverse shock (RS). For the first time we observe emission from the RS surface well above and below the equatorial ring (ER), suggesting a bipolar or conical structure perpendicular to the ring plane. Using the H imaging, we measure the mass flux of hydrogen atoms crossing the RS front, in the velocity intervals (−7500 < Vobs < −2800 km s−1) and (1000 < Vobs < 7500 km s−1), = 1.2 × 10−3 M yr−1. We also present the first Ly imaging of the whole remnant and new Chandra X-ray observations. Comparing the spatial distribution of the Ly and X-ray emission, we observe that the majority of the high-velocity Ly emission originates interior to the ER. The observed Ly /H photon ratio, 17, is significantly higher than the theoretically predicted ratio of 5 for neutral atoms crossing the RS front. We attribute this excess to Ly emission produced by X-ray heating of the outer debris. The spatial orientation of the Ly and X-ray emission suggests that X-ray heating of the outer debris is the dominant Ly production mechanism in SN 1987 A at this phase in its evolution.
UV observations made with the IUE satellite of Nova Her 1991 are presented and discussed. A distance of 3.4 kpc and reddening of 0.6 E(B-V) to Nova Her 1991 are determined by comparing its UV and ...optical outburst behavior with those of the extragalactic ONeMg nova LMC 1990 No. 1. Her 1991 was also detected by Rosat five days into its outburst, and it is argued that a small fraction of the X-rays may be the product of Comptonized 1.2 and 0.5 MeV emission from the decay of Na-22. If the mass of ejected shell is indeed as high as was estimated by Woodward et al. (1992), namely 0.0001 solar mass, then the present results predicted that Na-22 gamma-ray emission from the ejecta of Nova Her 1991 would still be detectable by GRO in the spring of 1992. The detection level was expected to be about 5 sigma in a two-week observation. Such a detection would strongly guide and constrain the hydrodynamic and nucleosynthesis simulations of nova outbursts on massive white dwarfs.
Cepheid Masses: FUSE Observations of S Muscae Evans, Nancy Remage; Massa, Derck; Fullerton, Alexander ...
The Astrophysical journal,
08/2006, Letnik:
647, Številka:
2
Journal Article
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S Mus is the Cepheid with the hottest known companion. The large ultraviolet flux means that it is the only Cepheid companion for which the velocity amplitude could be measured with the echelle mode ...of the HST GHRS. Unfortunately, the high temperature is difficult to constrain at wavelengths longer than 1200 AA because of the degeneracy between temperature and reddening. We have obtained a FUSE spectrum in order to improve the determination of the temperature of the companion. Two regions that are temperature sensitive near 16,000 K but relatively unaffected by H sub(2) absorption (940 AA and the Lyb wings) have been identified. By comparing FUSE spectra of S Mus B with spectra of standard stars, we have determined a temperature of 17,000 c 500 K. The resulting Cepheid mass is 6.0 c 0.4 M sub( ). This mass is consistent with main-sequence evolutionary tracks with a moderate amount of convective overshoot.
We observed supernova 1987A (SN 1987A) with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST) in 1999 September and again with the Advanced Camera for Surveys (ACS) ...on the HST in 2003 November. Our spectral observations cover ultraviolet (UV) and optical wavelengths from 1140 to 10266 AA, and our imaging observations cover UV and optical wavelengths from 2900 to 9650 AA. No point source is observed in the remnant. We obtain a limiting flux of F sub(opt) , 1.6 x 10 super(-14) ergs s super(-1) cm super(-2) in the wavelength range 2900-9650 AA for any continuum emitter at the center of the supernova remnant (SNR). This corresponds to an intrinsic luminosity of L sub(opt) , 5 x 10 super(33) ergs s super(-1). It is likely that the SNR contains opaque dust that absorbs UV and optical emission, resulting in an attenuation of 635% due to dust absorption in the SNR. Correcting for this level of dust absorption would increase our upper limit on the luminosity of a continuum source by a factor of 1.54. Taking into account dust absorption in the remnant, we find a limit of L sub(opt) , 8 x 10 super(33) ergs s super(-1). We compare this upper bound with empirical evidence from point sources in other supernova remnants and with theoretical models for possible compact sources. We show that any survivor of a possible binary system must be no more luminous than an F6 main-sequence star. Bright young pulsars such as Kes 75 or the Crab pulsar are excluded by optical and X-ray limits on SN 1987A. Other nonplerionic X-ray point sources have luminosities similar to the limits on a point source in SN 1987A; RCW 103 and Cas A are slightly brighter than the limits on SN 1987A, while Pup A is slightly fainter. Of the young pulsars known to be associated with SNRs, those with ages ,5000 yr are all too bright in X-rays to be compatible with the limits on SN 1987A. Examining theoretical models for accretion onto a compact object, we find that spherical accretion onto a neutron star is firmly ruled out and that spherical accretion onto a black hole is possible only if there is a larger amount of dust absorption in the remnant than predicted. In the case of thin-disk accretion, our flux limit requires a small disk, no larger than 10 super(10) cm, with an accretion rate no more than 0.3 times the Eddington accretion rate. Possible ways to hide a surviving compact object include the removal of all surrounding material at early times by a photon-driven wind, a small accretion disk, or very high levels of dust absorption in the remnant. It will not be easy to improve substantially on our optical-UV limit for a point source in SN 1987A, although we can hope that a better understanding of the thermal infrared emission will provide a more complete picture of the possible energy sources at the center of SN 1987A.
Careful deconvolution of spatially resolved IUE ultraviolet spectra shows that only two of the three stars detected in plate material before 1987 are now present near the site of SN 1987A. The ...separation, magnitudes, and spectra of these two are consistent with their identification as star 2 and star 3 of the Sanduleak -69 deg 202 trio. The clear implication is that star 1, the 12th mag B3 I star, has disappeared, and it may be identified as the progenitor of SN 1987A.
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